I. Field of the Invention
The present invention relates to internal combustion engines and, more particularly, to a carburetor and oil pump assembly for use in a chain saw and method of making the same.
II. Prior Art
Various different carburetors and chain oiling systems for use in chain saws are generally known in the art. One type of carburetor for use in chain saws is known as a diaphragm carburetor which is capable of maintaining a constant fuel pressure and thereby acts as a pressure regulating device to allow the chain saw to operate properly, even at relatively extreme or different attitudes or orientations and with pressurized gas tanks.
Various different lubricating systems for chain saws can be found in the prior art. U.S. Pat. No. 3,865,213 to McDermott describes an automatic pump for continuously pumping oil from a reservoir to a saw chain having a relatively small piston and a diaphragm which is actuated by pressure pulses developed in the crankcase of the engine. U.S. Pat. No. 4,644,658 to Dolata et al describes a working tool which is equipped with a device for interrupting the supply of oil to a tool which facilitates the use of chain saw apparatus with an accessory attachment tool such as a hedge trimmer, drilling tool or the like for which a flow of lubricating oil is unnecessary. U.S. Pat. No. 4,802,555 to Matsunaga et al describes a pressurized oil tank communicating with a crankcase of the engine where pressure forces oil from the oil tank to lubricate a saw chain. U.S. Pat. No. 2,944,538 to Conway et al describes a combined manual and automatic lubrication system for a chain saw that will assure an adequate flow of lubricant to the saw chain having a low pressure automatic lubrication system activated in response to a predetermined throttle position and a high pressure pump lubrication system selectively activated by an operator by depression of a manual pump plunger. U.S. Pat. No. 3,809,185 to Kobayashi et al disclosed an oil feed pump of a chain saw disposed in a chain saw crankcase. A cam portion of the crank shaft reciprocates the pump plunger so that oil passages which communicate with the cylinder bore delivers oil therein to be pumped to the point of use by the plunger. U.S. Pat. No. 3,332,411 to Bloom et al discloses a lubricating system for a power driven chain saw which automatically delivers a continuous flow of lubrication and which includes a selectively operated manual means to provide lubricant under relatively high pressure for clearing the lubricant passages from natural clogging after repeated usage. U.S. Pat. No. 3,010,538 to Strunk discloses a chain saw lubricating system having a pressurized oil reserve for providing oil to a saw chain. U.S. Pat. No. 2,605,787 to Kiekhaefer discloses a pressure lubricating system for an engine driven chain saw for delivery of oil to the saw chain during operation of the engine.
A continuing problem has existed with tools such as chain saws in that the number of parts and manufacturing and assembly methods generally make the manufacture and assembly of a tool relatively expensive, require additional quality controls, and adds weight to a hand held tool that can thus become heavy and cumbersome for an operator.
It is therefor an objective of the present invention to incorporate a chain oiler with a chain saw carburetor and supply the combined functions in a miniaturized and automatic assembly.
It is another objective of the present invention to provide a carburetor and oil pump assembly which is relatively easy to manufacture and assemble and which comprises relatively few parts.
It is another objective of the present invention to provide a carburetor and oil pump assembly which can be manufactured and assembled at a relatively reduced cost from that of prior art devices.
It is another objective of the present invention to provide a carburetor and oil pump assembly having fewer parts than prior art devices which greatly eases total chain saw assembly.
It is another objective of the present invention to provide a carburetor and oil pump assembly which can provide both chain oiling and engine oil injection and/or in carburetor blending of fuel mix with oil.
It is another objective of the present invention to provide a carburetor and oil pump assembly having a two-stage oil pump used to reduce close tolerance requirements required for a single stage priming while also affording relatively high chain oil pressure.